The Cold War emerged as the Soviet Union turned Eastern Europe - the invasion route to Russia for centuries - into a military and political buffer between it and the West. Each saw a different reality; The Soviets wanted troops in Eastern Europe to block an attack from the West; the West saw them as a prelude to an attack on the West. Mutual suspicion, misunderstanding, ideological posturing and rhetorical extravagance, and Soviet-style governments in the East locked the two sides in a tense standoff.
Marshal Josef Stalin makes a toast to Churchill on 30 November 1943, the British premier's 69th birthday, during the Tehran Conference. Stalin was a difficult ally and relations were not always this friendly. With Russia taking the brunt of the war against Germany, Stalin had aggressively insisted on an invasion of northern France. Churchill resisted. He believed that any premature 'Second Front' was likely to fail. At Tehran, a date was finally set for June 1944.
Winston Churchill took over as Prime Minister on 10 May, 1940, eight months after the outbreak of World War II in Europe. He had done so as the head of a multiparty coalition government, which had replaced the previous government (led by Neville Chamberlain) as a result of dissatisfaction with the conduct of the war, demonstrated by the Norway debate on the Allied evacuation of Southern Norway.[1] 

In this situation he found relief, as well as profit, in his pen, writing, in Marlborough: His Life and Times, a massive rehabilitation of his ancestor against the criticisms of the 19th-century historian Thomas Babington Macaulay. But overriding the past and transcending his worries about India was a mounting anxiety about the growing menace of Hitler’s Germany. Before a supine government and a doubting opposition, Churchill persistently argued the case for taking the German threat seriously and for the need to prevent the Luftwaffe from securing parity with the Royal Air Force. In this he was supported by a small but devoted personal following, in particular the gifted, curmudgeonly Oxford physics professor Frederick A. Lindemann (later Lord Cherwell), who enabled him to build up at Chartwell a private intelligence centre the information of which was often superior to that of the government. When Baldwin became prime minister in 1935, he persisted in excluding Churchill from office but gave him the exceptional privilege of membership in the secret committee on air-defense research, thus enabling him to work on some vital national problems. But Churchill had little success in his efforts to impart urgency to Baldwin’s administration. The crisis that developed when Italy invaded Ethiopia in 1935 found Churchill ill prepared, divided between a desire to build up the League of Nations around the concept of collective security and the fear that collective action would drive Benito Mussolini into the arms of Hitler. The Spanish Civil War (1936–39) found him convinced of the virtues of nonintervention, first as a supporter and later as a critic of Francisco Franco. Such vagaries of judgment in fact reflected the overwhelming priority he accorded to one issue—the containment of German aggressiveness. At home there was one grievous, characteristic, romantic misreading of the political and public mood, when, in Edward VIII’s abdication crisis of 1936, he vainly opposed Baldwin by a public championing of the King’s cause.
The following year was equally crucial, witnessing Germany’s attack on Russia and America’s entry into the war. Churchill had already established a warm relationship with President Franklin Roosevelt and put aside an instinctive dislike and distrust for Soviet premier Joseph Stalin. Churchill, a firm anticommunist, knew Stalin for what he was—unlike Roosevelt, who consistently made allowances for the Soviet dictator, fondly calling the genocidal despot ‘‘Uncle Joe.’’ Despite their personal and national differences with respect to communist Russia, Churchill and Roosevelt remained staunch allies throughout the war. They quickly decided on a ‘‘Germany first’’ strategy, but in early 1942 the main threat was from Japan, which was rolling up easy victories in the Philippines, Singapore, and Malaya.

Churchill Speech